Power boost surface control



Sept. 16 1952 c. SCHULTZ 2,610,314

POWER BOOST SURFACE CONTROLS Filed July 51, 1948 4 Sheets-Sheet 1INVENTOR.

Carl Schultz By @7763 TM AT TORNEY P 16, 2 c. SCHULTZ 2,610,814

POWER BOOST SURFACE CONTROLS '4 Sheets-Sheet 2 Filed July 31, 1948 canschunz,

ATTORNEY Sept. 16, 1952 c. SCHULTZ POWER BOOST summer: CONTROLS 4Sheets-Sheet 5 Filed July 31, 1948 l v l IIIIIIIIII 0| l 4],, all

mmvron. Carl schulll W77 {5. 6 (My ATTORNEY Patented Sept. 16, 1952POWER-BOOST SURFACE CONTROL Carl Schultz, Milford, Conn, assignor toUnited Aircraft Corporation, East Hartford, Conn.', a

corporationof Delaware Application u y 31, 1943, Serial No. 41,312

- 2 Claims. 1

This invention relates to surface control systems for aircraft andparticularly to surface control systems for low aspect ratio all-wingaircraft.

It is an object of this invention toprovide an improved surface controlsystemfor'aircraft in 'cluding two all-moving or unit tail; surfaceswhich replace the conventional elevators andv ailerons and to provide animproved operating mechanismfor moving these surfaces. eitherdifferentially, identically, orin some compromise manner by a singlepilotgcontrol member.

Another object of this inventionis to provide a combined leading ,tabinsuch ,a unit tail surface in combination with ,a power boost mechanism.

.A further object of thisinventionis to provide complete control of unittail surfaces .on ,a low aspect ratio all-wing airplane both as aileronsand-elevators by a single control column.

A still further object of this invention is to provide complete controlof unit tail surfaces on a low aspect ratio all-wing airplane bothuaselevators and ailerons by a single control column and a power boostmechanism; the boost me.ch-. anism having the properties of producinfeel forces in the control column in proportion to the aerodynamic loadsacting-on the :cont-rol surface.

Another object of this invention ,isctogprovide a power boost mechanismfor operatingaa unit controlsurface which hasla negative trailingtendency .in certainranges of deflection including a leading tabmechanism to-automaticallyreduce such negative oroverbalancedcharacteristics.

These and other objects .andadvantages of'the invention will-becomeevident from, the following specific descriptionof a preferredembodiment of the invention illustrated in the accompanying drawingswherein like reference numerals denote corresponding parts throughoutthe, .several views. f 1 1 r In thesedrawings, g

Fig. 1 is a perspective view 'of a low aspect ratio all-wing airplanehaving the control system of this invention, the airplane being. shownin phantom;

.Fig. 21 is an enlarged perspective. detail of the supportfor thecontrolfcolumnlandthe operating connectionsto thecolumn; I

Fig.3 is an enlarged perspective view showing thepower controlme'chanisniandleading tab linkages for'the unit control surfaces; I

Fig. 4 is an exploded View of the movable elements ofthe control'mechanismoffFlg'.

Fig.5 is a schematic diagram of:.-the hydraulic power boost systemindicating.the positionof the elements and the controlflsurfa'cewhenfthe systemjisin neutral; and I I Fig. 6 is similar toFigJE butindicates the po'-' sition of the power boost elements when the controlsurface is being deflected in one direction.

Reference is hereby made to Patent No. 2,585,411 dated February 12,1952, owned by the assignee of the present"applicationwhich disclosescommon subject matter.

Referring to Fig. ,1, the'numeral [0 indicates generally the main wingportion of the airplane which contains a pilot compartment l2, enginenacelles l4 and i6, and propeller mounting nacelles 22 and 24 whichproject forward of the leading edge of the wing near the lateral ex-,tremities thereof. The main wing I0 is provided with verticalstabilizing surfaces and 3 2 and is also provided with outwardlyprojecting control surfaces34 and 36 the trailing edges of which formextensions of the trailing edge 38 of the main wing Ill. The controlsurfaces 34 and 36 are provided with trailing edge tabs 40 and 42,respectively, which extend from the wing l0 outboard a substantialdistance along the length of the surfaces 34 and 36 and operateasleading or anti-boost tabs.

The pivoted control surfaces 34 and 36 and their pivoted trailing edgetabs 40 and 42 comprise all moving or unit control surfaces which areparticularly advantageous in low aspect allwing aircraft. Whereas theunit control surface when applied to the conventional airplane permitsthe use of a surface of less area than would be'possible by the use ofordinary elevator-stabilizer combination, the use of suchunit controlsurfaces in the all-wing low aspect ratio airplane shown hereinisparticularly advantageous because of extremely large range of angles ofincidence of the air-in the region of thesecontrol surfaces.

The airplane illustrated operates to an angle of attack range from zeroto degrees in power off flight andthe range from zero to -90 degrees inpower on flight. Incidence of the airin the region of the horizontaltail surfaces varies through a range of angles of the order-ofdegrees'relative to-the longitudinal axis of the aircraft. ySlip streameffects prevents it from exc'eeding this range inlpower on flight. Incomparison, a conventional airplaneoperates through anangle of attackrange of the order of 20 degreesand because of downwardieffects from themain airfo'il, the angle of the-air relative to the longitudinal-axisofthe aircraft in the regionof the'horizontal tail surfaces variesapproximately half this amount or through a range of 10 degrees.

With the conventional airplane it is hence possible to use a fixedstabilizerwith a con trollabletrailing edge airfoil asan-elevator- Onthe other hand, inthe -case of the low-aspect ratio all-wing airplaneillustratedpthe f-ull angle of attack range of the airplane cannot be 3identified with a conventional stablizer and a trailing edge elevatorunless the stabilizer is made adjustable through a wide range of anglesof the order of 30 degrees, this condition resulting from the wide rangeof angles of incidence of the ambient air in the region of the tailsurfaces. The use of a stabilizer adjustable through such a range makesit possible to trim the airplane through its performing speed range butthe controllability of the aircraft is still uncertain because of thenecessity of properly adjusting the stabilizer in order to effectmoderate or large changes in trim speed and the necessity of adjustingit during performance of maneuvers.

By using the unit tail surface area arranged to be rotatable through awide range of angles of the order of 70 degrees and by controlling therotation directly by the usual elevator control linkage, or the poweroperated range shown herein, it is made possible to trim the airplanethrough its entire speed range, power on or power off, and perform themost violent maneuvers through the use of this control alone. It is alsodesirable to use these same surfaces to provide lateral control of theairplane.

Principally then to achieve the wide control ranges necessary in anall-wing aircraft of this type it is desirable to pivot the controlsurface at approximately the 25 percent chord line. Such a controlsurface will have a trailing tendency with respect to the angle ofattack of the aircraft that is opposite to that of a common controlsurface; 1. e., in effect it has a negative trailing tendency whichurges the surface to increase its deflection toward an overbalancedposition. Under certain conditions the pilot forces required to restrainsuch overbalance become excessive or the power boost forces necessary tocontrol such overbalance become structurally excessive.

This undesirable overbalanced tendency is eliminated in a controlsurface of this type without altering the desirable characteristics byuse of leading or anti-boost tab; i. e., a tab that normally moves inthe same direction as the control surface but assumes a greater angulardeflection relative to the main wing than the control surface.

Thus as the control surface is deflected toward its maximum travel ineither direction the leading tab will deflect at a greater rate in thesame direction to balance the control surface in the unstable ranges. Asa result, as the overbalanced tendency increases in the control surfacethe balancing forces of the leading tab also increase.

To this end the unitary tail surfaces 34 and 36 are connected bysuitable operating connections with the pilot control column 48 locatedin the pilots compartment I2 so that these surfaces are movedidentically by fore and aft movements of the control column to providelongitudinal control of the airplane, the surfaces being moveddifferentially by lateral movement of the column to provide lateralcontrol of the airplane, or in compromise of these two movements byoblique movements of the control column.

The control column comprises a. hand grip 50, a stick 52, a socketassembly 54, a trunnion 56, a pair of depending forked arms 58, and auniversal assembly 60 shown most clearly in Fig. 2. The trunnion 56 hasits fore and aft pivotal axes 62 fixed at its extremities to fixedairplane structure (not shown) and has the socket as- 4 sembly 54pivotally mounted on its lateral trun nion arms 84. With thisarrangement it will be evident that the control column is mounted foruniversal movement about the intersection of the axis including arm 64and the fore and aft axis 62.

The forked arms 58 which are rigid with the socket arm 54 carry at theirdepending ends a U-shaped frame 66 which supports a generally horizontalrearwardly directed tongue 68 terminating in a ball 10 of the universalassembly 60. The ball I0 is located a sufficient distance below theintersection of the fore and aft axes 82 with the axis of the trunnionarms 64 to provide an adequate moment arm for moving the control linkageattached thereto in response to movements of the stick. The ball 10 isreceived in a suitable socket T5 at the forward end of a push-pull rod12 connected at its aft end to a sector wheel I3 (Fig. 1) which, throughsuitable cable connections, controls the left-hand unit surface 36. Asmiliar push-pull rod 14 having a yoke 16 at its forward end sultablypinned to the socket I5 of the rod 12 is pivotally connected at its aftend to a sector wheel 18 which controls the right-hand unit surface 34through suitable cable connections. It will be noted that the sectorwheels 13 and 18 are equally laterally spaced from the control columnand that push-pull rods 12, I4 connecting therewith diverge outwardlyand aft from the ball I0 on the low end of the control column. Thesector wheels I3 and "I8 are centrally pivoted at and 82, respectively,and have the aft ends of the rods I2, I4 pivotally connected thereto ateccentric points 83, 84 on adjacent inboard portions of the peripheriesthereof.

The unit control surfaces 34 and 36 and the mechanism by which they areoperatively conneceted to sector wheels 13 and 18 are identical exceptfor their left-hand and right-hand characteristics and accordingly adescription of the right surface 34 and its control mechanism will besuflicient for understanding of the invention.

The sector wheel 18 drives a hollow sector wheel 86 by means of cables81 and 88 which run over suitable pulleys 89, 80 and SI and have theiropposite ends connected to the ends of the sectors of wheels 18 and 86in a well-known manner to effect simultaneous and equal rotation ofthese wheels. It will be understood that to obtain the operationdescribed, the cables 81, 88 operatively connecting wheels I8 and 86 forsurface 34 are crossed, while the similar cables between wheels 13 andwheel 86 for surface 36 are not crossed, as will appear from Fig. 1. Thesector wheel 86 is rotatably mounted on a shaft 92 journalled inforwardly extending arms of a bracket 94 (Fig. 3) carried by fixedairplane structure adjacent the axis of pivotation on surface 34.

Rotation of sector 86 actuates a valve I00 to selectively directhydraulic fluid under pressure to the lines I02 and I04 leading toeither side of the pair of actuating struts I06 and I08 whose piston rodends H0 and H2, respectively, are fixed to the aircraft structure. Itshould be noted here that struts I06 and I08 are interconnected and assuch act as a unit. The valve I00 and a cooperating feel strut I I 4 ofa conventional cylinder and piston .type are located within the hollowwheel 86 and have their remote ends pivotally connected to the wheel atH6 and H8, respectively. Their adjacent ends are connected to a pin I20which connects the apex of the triangular plates HI and I22 disposed oneither side of the sector wheel 86. The triangular plates I2I and I22are pivoted on shaft 82ata point in the center of the base of each ofthese plates. The free corners of the plates I2I and I22 which are abovethe shaft 62 are, pivotally connected by means of rods I23 and I24 withthe upper arms of horn I26 fixed to a torque tube I28 which is rotatableabout the axis of pivotation of surface 34 and has this surface rigidlyaflixe'd thereto by a mounting bracket I36. The lower free corner ofplates I2I and I22 are-similarly connected to the lower arms of horn I26by rods I32 (only one of which is shown). A pair of brackets I36 aredisposed on either side of the sector wheel 86, one bracket beingfastened to the plate I2I and the other to the plate I22. Each bracketalso has a pivotal connection with the shaft 92. Each of the bracketsI36 has a bifurcated upper end for receiving an adapter I36 which ispivotally connected thereto and carries the relatively free end of eachof the actuating struts I66 and I68. It is then apparent that when thestruts I66 and I68 are controllably actuated by means of the valve I66they impart movement to the brackets I36 and the plates I2 I, I 22fastened thereto. In turn the plates I2 I, I22 through the connectingrods I23, I24 and I32 will pivot the horn I26 and rotate the torque tubeI28 so as to move the control surface 34 which is The operation of therigidly connected thereto. I valve I66 and the feel strut Il4 will bemore fully described in connection with Figs. 5 and 6.

Upon movement of the controlsurface 34 a leading tab mechanism issimultaneously placed in operation. Under these conditionsthe motion ofthe cable sector 86 is imparted by the boost mechanism to the horn I26as above described which in turn imparts rotational movement to a bellcrank supporting member I46 which is coaxially disposed with respect tothe horn and is fixed thereto inboard of the torque tube I28 so as torotate in unison and therewith (better seen in Fig. 4). A bell crank I42has one corner pivoted to the support I46 at I44 and has another cornerthereof pivotally connected at I46 to control rod I48 which extendsaxially through the torque tube I28 and is pivotally connect'ed at itsoutboard end to a bell crank I56 (Fig. 1) which has its other free armconnected by a link I52 to one of the horns, I54 of tab 46. Another hornI56 is connected by a parallel link I58 to a bell crank I66 which isoperated by an extension I62 of rod I48. Thev third corner of bell crankI42 (Fig. 4) is pivotally attached at I66 to one end of rod I68, theother end of which is pivotally attached at I16 to a lever I12. Thelever I12 is centrally pivoted at a point I14 on another lever I16 theupper end of which is pivoted to fixed structure of the airplane at I18and the lower end of which is adjustably fixed by means of link I86 tothe trim tab adjusting mechanism I82. A connector I84 serves topivotally fix the lower end of lever I12 to aircraft structure adjacentthe trim tab adjustingmechanism I62.

'I'hus it is evident that when the trim tab adjusting mechanism is notbeing operated the lever I16 which carries the pivot point I14 for leverI12 is considered fixed and the operation of the tab 46 as a leading tabis a function of the geometry of the tab operating linkage. It isreadily apparent that rotation of horn I26 to move the surface 34 alsoresultsin similar rotation of tab operating rod I48 and bell cranksupport I46 and that the bell crank I42 carriedzby the latter is rotatedbodily therewith. Thefixed point I14 is, however, spaced from the axisof rotation of these parts and as a :result the bodily rotation of thebell crank I42 about this axis causes the bell crank to rock about itspivotal support I44 and impart a reciprocating movement to rod I48.Thus, referring to Figs. 3 and 4, ifthe sector wheel 86 is moved in acounterclockwise direction as indicated bythe arrows, the valveI66.wi1l-be actuated so as to direct fluid to the actuating struts I66,I68 which impart motionin the same direction to the upper ends of platesI2], I22 and also impart counterclockwise motion to the horn I26 bymeans of the connections therewith through rods I23, I24 and I32.counterclockwise motion of the horn I26 andlits integral torque tube I28will cause the trailing portion of the control surface 34 to be movedupwardly. At the same time the bell crank support I46 will rotate bellcrank .I 42 which in turn will simultaneously pivot about I44 and movethe control rod I48 inboard. The outboard end of control rod I48beingconnected to one free end of the bell cranks l56and I66 will draw thelinks I52 and I58 forward so that ,the tab 46 will also be movedupwardly. I The geometry of the 'tab mechanism is such that the trim tab46 will be displaced in the same direction ,asthe control surface 34 butat a greater angularrate than the surface 34 in relation to the mainwing.

The operation of the valve I66, the feel strut H4, and the actuatingstruts I06, I68 is better understood by referring to theschematicdiagram in Fig. 5. Hydraulicfluid under, pressure can be admitted to thevalve I66 through the line 266 while the line 262 provides a return linefrom the mechanism In this position of the valve I66 it will be notedthat the lands .264 and 2.66 within the valve I66 cover the ports leadinto the lines I62 and I64 so that the pistons in thestruts I66, I68 willbe locked in position. In this neutral position of the valve I66 no.motion is imparted to the surface 34. The feel strut H4 isproportionately smaller than the actuating struts I66, I68 and has eachof itsends in :fluid communication with one of the lines I62, I64. Thuswhen fluid under pressure is being directed to either side of theactuating struts I66, I 68, a cer--' tain amount of fluid will entereither side of the feel strut II4 thereby introducing forces within theboost mechanism which tend to resist any motion of the sector wheel 86and provide acertain amount of feel to the pilots control member 48.Since the feel strut H4 is smaller than the actuating struts I 66, I68only a small resisting forcewill be applied at the connection H8 on thesector wheel 86. I

Thus when it is intended to move the surface 34 upwardly the pilot movesthe control stick 48 so that the control cable 81 is moved in thedirection of the arrowshown in Fig. 6. Movement of the control cable 81will rotate the sector wheel 86 counterclockwise so that the control rod2I6 of the valve I66 will move thelands 264 and 266 to the positionwherein the ports leading .to lines I62 and I64 are open. Fluidunder'pressure will then be admitted to the line I62 from line 266tending to move the strut I68 and the strut I66 (not shown in thisfigure) to the left as indicatedby the arrow so that through the pivotedconnections the control surface 34 will be moved from the dotted to thefull line position. At the same time fluid under pressure will also passvia the line 2 I2 into the lower end of strut I I4 tending to move thestrut in opposition to the motion imparted originally to the sectorwheel86 thereby creating a proportionate resisting force or feel in thecontrol system. Additionally, as the surface reaches the desiredposition and the sector wheel motion ends (as a result of the release ofpressure by the pilot), the feel strut Ill acts as a follow-up tendingto move the pivot connection I20 toward a position of neutrality whereinthe control valve I will again assume the position shown in Fig. to holdthe surface in locked position. Thus to return the control surface toits neutral position it is necessary to reverse the motion of the sectorwheel 86 to reverse the direction of flow of fluid in the system. Underthese conditions the feel force in the system is similarly created asdescribed above and the follow-up valve neutralizin action commencesupon release of pressure on the controls by the pilot.

It will be noted that the control rod 2 I0 in the valve I00 has a,drilled passage 2I6 which via the ports 2I8 and 220 permits fluidcommunication between the outboard side of the lands 204, 206 so thatthe lines I02 and I04 can function either as pressure or return lines.

As a result of this invention a control system has been provided inwhich both longitudinal and lateral control is obtained by actuation ofa single pilot operated control member and wherein both a power boostand leading tab mechanism is provided. It is further evident that as aresult of this invention a power boost mechanism has been provided incombination with the foregoing wherein a control surface havingoverbalanced tendencies is properly balanced in its unstable ranges by aleading or anti-boost mechanism which is synchronized to take effect inproportion to the relative displacement of the control surface.

Further as a result of this invention a power boost mechanism has beenprovided for moving unit control surfaces of the type described whereinproportionate feel forces are provided in the system by a feel strutwhich also operates as a valve neutralizer to hold the surface in anydeflected position.

While only one embodiment of the invention has been shown and disclosedherein, it will be understood that numerous changes in the constructionand operation of the parts may be made without departing from the scopeof this novel concept.

Iclaim,

1. In an airplane, a main lifting surface, two control surfaces mountedon opposite sides of the fore and aft center line of said main surface,a pilot operated control member having two different movements, ahydraulic power boost strut connected to each of said control surfacesfor moving the latter identically in response toone of said movements ofsaid control member and in opposite directions in response to the otherof said movements, said power boost struts operating said surfacessimultaneouslyin response to either movement of said control member, andcontrol mechanism interposed between said control member and each ofsaid power boost struts including a sector wheel operatively connectedto said control member, a feel cylinder having one of its ends attachedto said sector wheel, a selector valve attached to said sector wheel andoperated by movement of the same for directing pressure fluid from areservoir to either end of its associated power boost strut and forsimultaneously directing pressure fluid of a lesser amount to said feelcylinder from said reservoir for producing forces resisting movement'ofsaid control member proportionate to but less than the forces producedby said associated power boost strut, an operative connection betweensaid associated power boost strut and said valve for returning thelatter to its non-selective positions whereby the control surfaceassociated with said associated power boost strut is hydraulicallylocked in the position of deflection corresponding to the degree ofmovement of said control member, and an operative connection betweensaid feel cylinder and said associated power boost strut and said valvewhereby said resisting forces are made inoperative when said valve isreturned to its non-selective position.

2. In an all-wing tailless type airplane, a major lifting surface, twoaerodynamically unstable control surfaces laterally disposed from thefore and aft center line of said lifting surface, a single pilotoperated member for moving said surfaces identically and in oppositedirections with respect to said lifting surface to effect longitudinaland lateral control respectively, a hydraulic power boost strutconnected to each of said surfaces, mechanism between said member andeach of said power boost struts including a sector wheel adapted to berotated by said member, a feel strut attached to said sector wheel, aselector valve governed by the rotation of said sector wheel forselectively directing pressure fluid from a reservoir to its associatedpower boost strut for activating the same and for directing pressurefluid but of a lesser amount than that directed to said associated powerboost strut to said feel strut for producing forces resisting movementof said sector wheel and said pilot operated member proportionate to butless than the forces produced by said associated power boost strut,follow-up means governed by said associated power boost strut forreturning said selector valve to a neutral position while said sectorwheel is maintained in a rotated position, and a linkage connectionbetween said follow-up means and said feel strut for neutralizing saidresisting forces when said selector valve is returned to its neutralposition, and leading tabs responsive to movement of said surfaces forestablishing conventional forces on said surfaces in unstable attitudes.

CARL SCHULTZ.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,140,037 Swisher Dec. 13, 19382,222,886 Voigt Nov. 26, 1940 2,366,382 Burton et a1 Jan. 2, 19452,406,588 Cornelius Aug. 27, 1946 2,416,958 Sears Mar. 4, 1947 2,430,808Eaton Nov. 11, 1947 FOREIGN PATENTS Number Country Date 670,085 FranceAug. 12, 1929

